Known camera viewfinders are provided with means for adjusting the image field to those of the lens of the camera. For example, still cameras are provided with viewfinders whose entrance apertures can be altered by changing the mask and adapted to the various focal lengths of the lenses used in the camera. Each mask aperture however corresponds only to a certain focal length setting.
In photographic cameras featuring lenses with continuously changing focal length, i.e. so-called zoom lenses, it is desirable to have continuously changing viewfinders too, that are linked to the zoom lens such that the image field observed in the viewfinder corresponds precisely to that of the light-sensitive surface of the film.
Viewfinders provided with continuously adjustable framing masks and capable of connection to zoom lenses are known, for example from DE-PS-12 14 079. The known masks, in which all four sides of the frame are simultaneously adjustable, require however complicated devices that prohibit a simple and dependable mode of operation. Furthermore, devices of this complexity are relatively expensive and not suitable for use in cameras of very simple design, such as so-called single-use cameras.
The use of a viewfinder not adjusted to the lens focal length leads to unacceptable photographic results when it is remembered that wide-angle lenses have an angle of view exceeding 90.degree., while telephoto lenses have less than 25.degree..